Islamist extremists in Iraq are shooting and killing civilians as they attempt to flee fighting between the Islamic State group and Iraqi government forces in the city of Fallujah, the Norwegian Refugee Council said.

“Reports from families that NRC has been in touch with describe that civilians trying to cross the Euphrates River in order to flee the fighting are being targeted by armed opposition groups,” the human rights group said in a statement.

Iraqi forces have been battling with the IS fighters for a few weeks in an effort to retake the city, which has been controlled by the Muslim group since January, 2014. The offensive has so-far surrounded the city on three sides, with the only area remaining unclaimed being the western bank of the Euphrates.

Smoke rises after an airstrike by U.S led coalitio
Smoke rises after an airstrike by U.S led coalition warplanes, as Iraq's elite counterterrorism forces enter Shuhada neighborhood in Fallujah, Iraq, June 5, 2016.

50,000 civilians trapped

A U.N. estimate puts the number of civilians trapped in Fallujah at around 50,000. People have been attempting to cross the river as a means of escape, but the U.N. said several people, including children, have drowned while attempting to traverse the 300 meter-wide river.

According to the NRC, just under 3,000 families successfully escaped from Fallujah during the early days of the Iraqi offensive, which began on May 21. Since then, the group said, only a few families have been able to escape.

"Our biggest fears are now tragically confirmed with civilians being directly targeted while trying to flee to safety,'' Nasr Muflahi, the NRC country director in Iraq, said. "This is the worst that we feared would happen to innocent men, women and children who have had to leave everything behind in order to save their lives.''

The Fallujah offensive coincides with two other strikes on IS-held cities in neighboring Syria. Syrian government troops have begun retaking the city of Raqqa, while Syrian Kurdish fighters have advanced on the city of Manbij, a key IS stronghold near the Turkish border.

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